Due to an increasing reliance on large-volume data transfers, there is an increasing need to accurately measure operational performance of data communications networks. Communications networks, especially packetized data networks, are currently utilized in various applications for transmission and reception of data between parties at different locations. A typical data transmission system includes a plurality of end user sites and a data packet switching network, which resides between the sites to facilitate communications. Each site is connected to the switching network via an access channel (i.e., a channel connecting a site to a communications system), wherein transmission circuits, preferably virtual circuits, establish paths between the sites through the access channel and the switching network.
Packetized data networks typically format data into packets for transmission from one site to another. In particular, the data is partitioned into separate packets at a transmission site, wherein the packets usually include headers containing information relating to packet data and routing. The packets are transmitted to a destination site in accordance with any of several conventional data transmission protocols known in the art (e.g., Asynchronous Transfer Mode (ATM), Frame Relay, High Level Data Link Control (HDLC), X.25, IP tunneling, etc.), by which the transmitted data is restored from the packets received at the destination site.
Packetized data communications are especially appealing for common carrier or time-shared switching systems, since a packet transmission path or circuit is unavailable only during the time when a packet utilizes the circuit for transmission to the destination site, thereby permitting other users to utilize that same circuit when the circuit becomes available (i.e., during intervening periods between packet transmissions). The access channel and each individual transmission circuit typically have a maximum data carrying capacity or bandwidth that is shared among the various users of the network. The access channel utilization is typically measured as an aggregate of the individual circuit utilizations and has a fixed bandwidth, while the individual circuits may be utilized by several users wherein each user may utilize an allocated portion of the circuit.
Various systems have been proposed which provide some measure of network system performance. Specifically, a number of techniques for measuring round trip delay (RTD) of data transmitted between two sites is known. For example, U.S. Pat. No. 5,521,907 to Ennis, Jr. et al., the disclosure of which is incorporated herein by reference in its entirety, discloses a system for passively measuring the round trip delay of data messages sent between two sites. More specifically, a console triggers probes at two sites to store data packets being sent between the two sites. The probes generate unique packet signatures based on the data in the packets, and time stamp the signatures. By matching signatures from the two probes and comparing the corresponding timestamp values, the console can determine the round trip delay between the sites. This technique requires the storage, transmission and processing of a significant amount of data, particularly if implemented to periodically monitor all virtual circuits existing between a set of sites. That is, the passive probes cannot individually determine round trip delay, and each probe must store and transmit a substantial amount of data to the console which is required to correlate signature and timestamp data from different sites.
U.S. Pat. No. 5,450,394 to Gruber et al., the disclosure of which is incorporated herein by reference in its entirety, discloses a technique for determining round trip delay in which measurement cells containing timestamp information are sent between two nodes. A first node transmits a measurement cell with a first time stamp to a second node, and the second node replies with a measurement cell containing additional time stamp information which can be used by the first node to determine the round trip delay. Because the technique relies, in part, on timestamps already present in PM OAM (performance management operations, administration and maintenance) ATM cells, the technique is specific to the ATM protocol and cannot readily be adapted to other data protocols or be expanded to monitor other service level performance metrics. Further, the technique does not allow both nodes to measure the round trip delay of the same sequence of cells (i.e., either only one of the two nodes measures round trip delay or the two node measure delays of different transmitted cell sequences).
Further, while it is possible for individual switches in existing network systems to indicate how many packets of data have been dropped by the switch, there are no known systems capable of measuring a rate of successful (or unsuccessful) data delivery on a service level, e.g., over a particular virtual circuit or to a particular end user.
The problem of providing service level analysis of network performance is complicated by the fact that many switching networks comprise interworked systems using plural, different data transmission protocols (e.g., an ATM switching network interworked with a Frame Relay switching network), thereby forming a so-called “interworked” network. Such interworked networks are becoming more common, and present an additional challenge to designing a service level analysis tool that employs a standard message structure and messaging protocol useful for communicating between any two sites. Existing systems relying on inter-site or inter-probe messages to assess system performance are generally incapable of operating across interworked networks.
Current performance monitoring techniques involve the use of ‘ping’, ‘traceroute’, ‘netperf’, data accessed through SNMP, etc. These methods are disadvantageous in that they add extra traffic load in the network between all of the access points. These methods also add additional packet processing on the network routers. These traditional network performance measurement mechanisms tend to be relatively heavy weight and generally rely on sending a continuous sequence of ping packets or other network probes between an end-point to all the other end-points. This process creates a large increased load on the network. The traditional normally high overhead network performance measurement mechanisms are herein referred to as ‘heavy weight’ mechanisms.
A typical ISP or a corporate intranet backbone has a very large number of network end-points. It is not typical to have a continuous monitoring of network performance between all of the end-points. The problem is compounded by the fact that the access points that may be controlled by the network operator are usually intermediate points in the network, and do not constitute either the source or destination of the traffic.
It is also known that data transfer performance between two points may differ depending on the direction of the data traffic. Where communication in one direction may be relatively efficient, communication in the reverse direction may be inefficient.
Often, identical data is stored or “mirrored” on multiple different systems, all of which are accessible over the same network. If a client system must read from or write to the mirrored data, it is advantageous to have the client system access the mirror system with which it has the most efficient connection. It is possible that one mirror system provides the most efficient data transfer TO the client system, while another mirror system provides the most efficient data transfer FROM the client system.
Accordingly, there remains a need for a system and method for analyzing network traffic between a client system and multiple mirror systems, to determine the most efficient data transfer paths for accessing the mirrored data.